/*
 * @(#)img_ordclruns.h	1.10 06/10/10
 *
 * Copyright  1990-2008 Sun Microsystems, Inc. All Rights Reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER
 * 
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License version
 * 2 only, as published by the Free Software Foundation. 
 * 
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License version 2 for more details (a copy is
 * included at /legal/license.txt). 
 * 
 * You should have received a copy of the GNU General Public License
 * version 2 along with this work; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA
 * 02110-1301 USA 
 * 
 * Please contact Sun Microsystems, Inc., 4150 Network Circle, Santa
 * Clara, CA 95054 or visit www.sun.com if you need additional
 * information or have any questions. 
 *
 */

/*
 * This file contains macro definitions for the Encoding category of
 * the macros used by the generic scaleloop function.
 *
 * This implementation uses an ordered dithering error matrix to
 * produce a moderately high quality version of an image with only
 * an 8-bit (or less) RGB colormap.  The ordered dithering technique
 * does not rely on the order in which the pixels are processed so
 * this file can be used in cases where the ImageProducer has not
 * specified the TopDownLeftRight delivery hint.  The ordered dither
 * technique is also much faster than the Floyd-Steinberg error diffusion
 * algorithm so this implementation would also be appropriate for
 * cases where performance is critical such as the processing of a
 * video stream.
 *
 * This file can be used to provide the default implementation of the
 * Encoding macros for RGB colormapped displays.
 */

/*
 * These definitions vector the standard macro names to the "Color"
 * versions of those macros only if the "DitherDeclared" keyword has
 * not yet been defined elsewhere.  The "DitherDeclared" keyword is
 * also defined here to claim ownership of the primary implementation
 * even though this file does not rely on the definitions in any other
 * files.
 */
#ifndef DitherDeclared
#define DitherDeclared
#define DeclareDitherVars	DeclareAllColorDitherVars
#define InitDither		InitColorDither
#define StartDitherLine		StartColorDitherLine
#define DitherPixel		ColorDitherPixel
#define DitherBufComplete	ColorDitherBufComplete
#endif

#define DeclareAllColorDitherVars			\
    DeclareColorDitherVars				\
    int relx, rely;

#define DeclareColorDitherVars				\
    extern uns_ordered_dither_array img_oda_red;	\
    extern uns_ordered_dither_array img_oda_green;	\
    extern uns_ordered_dither_array img_oda_blue;

#define InitColorDither(cvdata, clrdata, dstTW)			\
    do {} while (0)

#define StartColorDitherLine(cvdata, dstX1, dstY)		\
    do {							\
	relx = dstX1 & 7;					\
	rely = dstY & 7;					\
    } while (0)

/*
 * The adjustments below are gross, but they are required due to
 * the way color lookups are done.
 * The second set of adjustments simply clips the values generated
 * by the ordered dithering values to a limit of 256 which represents
 * full intensity.
 * The first set of adjustments prepares for the fact that when
 * the final lookup is done, maximum intensity is represented by
 * the value 256, but the input values go from 0 to 255.  As a
 * result, the maximum input intensity needs to be mapped from
 * 255 to 256.  The Floyd-Steinberg lookups use a rounding
 * calculation to handle mapping the values near 255 to the maximum
 * intensity, but ordered dithering uses a truncating calculation
 * so the value 255 will be rounded down to the second highest
 * intensity thereby causing an occasionaly dark pixel when rendering
 * the maximum input intensity.  Other intensities (less than 255)
 * are left alone since modifying them would slightly disturb their
 * error distribution.  In particular, for red, the value 0xe0 has
 * a maximum error of 0x1f added to it which must not be mapped to
 * the maximum intensity since intensity 0xe0 can be represented
 * exactly.  So, a calculated 0xff (0xe0 + 0x1f) needs to be left
 * less than 256, but a natural 255, or a calculated (>=) 256
 * should be mapped to maximum intensity.
 */
#define ColorDitherPixel(dstX, dstY, pixel, red, green, blue)	\
    do {							\
	if (red == 255) {					\
	    red = 256;						\
	} else {						\
	    red += img_oda_red[relx][rely];			\
	    if (red > 255) red = 256;				\
	}							\
	if (green == 255) {					\
	    green = 256;					\
	} else {						\
	    green += img_oda_green[relx][rely];			\
	    if (green > 255) green = 256;			\
	}							\
	if (blue == 255) {					\
	    blue = 256;						\
	} else {						\
	    blue += img_oda_blue[relx][rely];			\
	    if (blue > 255) blue = 256;				\
	}							\
	pixel = ColorCubeOrdMapUns(red, green, blue);		\
	relx = (relx + 1) & 7;					\
    } while (0)

#define ColorDitherBufComplete(cvdata, dstX1)			\
    do {} while (0)
